We consider polynomials orthogonal on $[0,\infty)$ with respect to
Laguerre-type weights $w(x)=x^\alpha e^{-Q(x)}$, where $\alpha>-1$ and where
$Q$ denotes a polynomial with positive leading coefficient. The main purpose of
this paper is to determine Plancherel-Rotach type asymptotics in the entire
complex plane for the orthonormal polynomials with respect to $w$, as well as
asymptotics of the corresponding recurrence coefficients and of the leading
coefficients of the orthonormal polynomials. As an application we will use
these asymptotics to prove universality results in random matrix theory.
We will prove our results by using the characterization of orthogonal
polynomials via a $2\times 2$ matrix valued Riemann-Hilbert problem, due to
Fokas, Its and Kitaev, together with an application of the Deift-Zhou steepest
descent method to analyze the Riemann-Hilbert problem asymptotically.